Minimum orbital separation from SMT evolution is different for different types of donor stars. Top left: Evolution of the mass transfer rate (Ṁ) as a function of the decreasing binary separation in interacting systems with a BH accretor and a 30 M_⊙ donor of different donor types. The CHeB donor is the same ∼250 R_⊙ giant as in Fig. 9, whereas its HG variant comes from the grid with low semiconvection. The solid lines are models at q = q_crit, dashed lines are at q slightly larger than q_crit, such that the MT becomes unstable (star symbols). Right: Internal entropy and H abundance profiles of different donors from the onset of RLOF, plotted as a function of the internal mass coordinate m. The He-core in post-MS donors is at m ≲ 13 M_⊙. The layers that cause the Ṁ peak and dynamical instability (star symbols) are where the entropy profile is nearly flat. Bottom left: Same entropy profiles but as a function of the radial coordinate. The difference in the location of the constant entropy regions in the envelopes of different donors is primarily responsible for different minimum orbital separations a_min that may be reached via SMT.